Multistage ejector



J. SIM

MULTISTAGE EJECTOR April 27, 1937.

Filed No.' 25, 1935 ngi atentecl pr. 27, 1937 UNITED STATES PATENT OFFICE MULTISTAGE EJECTOR James Sim, Cathcart,

signor to G. & J.

Glasgow, Scotland, as- Weir, Limited, Glasgow,

Scotland, a corporation of Great Britain 1 Claim.

This invention relates to improvements in multi-stage steam-jet ejector installations for extracting air and vapor from condensers, and aims to provide an improved arrangement in which losses incurred in transformation of pressure and velocity are minimized.

A multi-stage steam-jet ejector installation according to the present invention comprises an aligned series of ejector nozzles and diffusers so arranged that the downstream nozzle or each downstream nozzle of the series is located adjacent to the exit of a diiuser throat for reception of inducing uid from said throat, so that the inducing fluid enters the downstream nozzle o1' each downstream nozzle with a velocity substantially equal to the velocity iin the throat discharging thereinto.

A multi-stage steam-jet ejector installation constructed in accordance with the present invention is illustrated in axial section in the gure of the accompanying drawing.

The ejector installation shown comprises an aligned series of three steam-jet ejectors, including the nozzle l of a rst-stage ejector which draws .air and vapor from a main condenser (not shown) and discharges into a rst inter-condenser, the nozzle 2 of a second-stage ejector drawing from the rst inter-condenser and discharging into a second inter-condenser, and the nozzle 3 of a third-stage ejector drawing from the second inter-condenser and discharging into an .after-condenser, said third-stage ejector nozzle 3 being supplied with high pressure steam by Way of a pipe 5. The rst and second inter-condensers and the after-condenser are constituted by compartments of a condenser casing 4. The nozzles l, 2, which are downstream of the nozzle 3, are arranged at the exits of diffuser throats 2a, 3a, respectively, discharging thereinto, said throats opening into radially-diverging diffuser chambers 2b, 3b piped to the second inter-condenser and to the after-condenser, respectively.

It will be understood that the chambers 2b, 3b may, if desired, be of the conically diverging annular type.

Since the iirstand second-stage nozzles l, 2 are respectively located at the exits from the diffuser throats 2a, 3a discharging thereinto, the steam entering these nozzles has a velocity approximating to the dilfuser throat velocity, which Vvelocity is approximately equal to the velocity of sound. The speed of the steam leaving either of the nozzles l, 2, therefore, is that due to the prese sure drop which occurs across the respective nozzle, plus the diiuser throat velocity; there is thus no loss incurred due to the diifuser throat velocity having to be transformed into pressure and then retransformed into velocity. An enhanced performance is, therefore, obtained.

By way of example, in the embodiment under consideration, the pressure in the diffuser throat 3a of the third-stage may be about 8.5 lbs. per square inch. The steam which leaves the second-stage nozzle 2 will have a velocity corresponding to the pressure drop, plus an additional velocity of about 1,382 feet per second, which is the diffuser throat velocity corresponding to 8.5 lbs. per square inch. Similarly, the exit velocity from the first-stage nozzle I will be that due to the pressure drop from the second diffuser throat pressure of 1.53 lbs. per square inch, plus an additional velocity of about 1300 feet per second, which is the second diffuser throat velocity corresponding to 1.53 lbs. per square inch. With a Vacuum of 29 inches of mercury at the firststage, the second-stage vacuum will be 28 inches, and the third-stage 24.5 inches.

'I'he pressure at the iirst-stage diiuser throat Ia will be 0.75 lb. per square inch, the pressure at the second-stage difuser throat 2a 1.53 lbs. per square inch, and the pressure at the third-stage diffuser throat 3a 8.5 lbs. per square inch.

I claim:

A multi-stage steam-jet ejector installation comprising an aligned series of ejector stages including an upstream ejector stage and a plurality of ejector stages located downstream of said upstream ejector stage, each ejector stage comprising a nozzle and a diffuser presenting a diffuser chamber and a throat opening into said diffuser chamber, the entrance end of the nozzle of each downstream ejector stage being located in such immediate proximity to the exit of the throat of the diffuser of the immediately preceding stage that the velocity of the jet through such nozzle is substantially equal to the velocity in the throat of the diiuser immediately upstream of such nozzle, a passage connecting each ejector stage with the discharge of the stage immediately downstream thereof, and a connection for supplying high pressure steam to the furthest upstream nozzle of the series.

JAMES SIM. 

